The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 20, 1990
Filed:
Nov. 07, 1988
Bruno A Rist, Woodland Hills, CA (US);
Adrian J DeVries, Aurora, IL (US);
International Telesystems, Inc., Beverly Hills, CA (US);
Abstract
A Television Signal Transmission Security System which provides a higher degree of security then previously possible by utilizing encoding and decoding technology which effectively prevents pirating by amateurs or experimenters. The television signal transmitted is encoded by injecting one or more modulated interfering signals in specific frequency slots in close proximity to the video carrier. Continuous or alternating interfering signals can be injected either above or below the video carrier between harmonics of the horizontal frequencies. Combinations of interfering signals provide coding techniques making the system virtually pirate proof. The interfering signal is removed by very narrow band rejection filters having a rejection band attenuation greater than about 40 dB over a bandwidth equal to the bandwidth between adjacent harmonics of the horizontal sweep frequency. The filters are constructed using advanced technology to produce the quartz crystal bulk resonators or surface acoustic wave filters. Pre-compensation at the transmitter improves overall amplitude and phase response to provide a nearly perfect decoded picture.